Automatic Signaling, Train Stop, and Route Interlocking Installed in The

252 View of track along a station platform with an automatic sign a 1 at t h e right Below - Motorman operating the release at an automatic signal Automatic Signaling, Train .Stop RouTE No. 1 of the Chicago Subway system, placed in service in October, 1943, includes modern automatic block signaling, automatic train-stop equipment, and 3 all-relay route control interlockings. This Route No. 1, the first portion of a proposed ex tensive subway system, connects witl1 the North Side Elevated Lines near Armitage and Sheffield avenues, ex tends southeast in Clybourn avenue, east in Division street and south in State street to a connection with the South Side Elevated Lines near Seventeenth street, the total length of the double-track subway being 4.9 miles. Route No. 2, which is 3.85 miles long, connects with the North west Elevated Lines near Milwaukee and Evergreen avenues, extends southeast in Milwaukee avenue, east in Lake street, and south in Dearborn street, where it is to continue west in Congress street to a loop east of the river. This route No. 2, now about 80 per cent complete, wi ll be fini shed as soon as war conditions permit. Plans for future subways include al- 253 Automatic signaling for 40 trains each hour includes time dis t ance-speed con trois on decend ing grades and on approach to stations Three interlockings are· especially de signed fo r rapid change of line-up Panel of the UR in terlocking machine at the South Portal includes four main tracks, the two center tracks for express trains and the two outside tracks for local trains. The subway is double track and all trains stop at all stations. In order that trains from any of the four tracks from the north can be routed to either track in the subway or vice versa, the track layout at the north portal was designed with crossovers and Route Interlocking and switches, as shown in Fig. 2, in which the tracks from the subway emerge on an ascending grade as the Installed in the Chicago Subways two middle tracks, with two elevated tracks on each side. This layout in cludes 8 crossovers, 2 single switches and 34 signals, which are controlled most 42 miles of additional subways whereas the elevated crosses the river by an all-relay route-control ma to be constructed as finances become on a drawbridge, and quite often this chine in a tower at Armitage avenue. available. bridge has to be raised for the passage South of the south portal at Seven of a boat, with the result that trains teenth street, the South Side Ele Utilization of Route No. 1 operating on the elevated structures vated has three tracks, one track on are seriously delayed. each side is for local stops as well as The purpose for these subways is Since the subway was placed in for certain through trains, while the to extend local rapid transit facilities, service, the traffic has increased rap center track is fo r through express expedite train movements and ulti idly, not only because of the improved trains between Seventeenth streetand mately to permit the removal of the service, but also due to the fact that Indiana avenue, this track being used elevated track structure in the down the rationing of tires and gasoline has in one direction or the other depend town area. The "L" trains now oper forced many persons to abandon ing on the preponderance of traffic ; ating through subway Route No. 1 automobile transportation and use the for example, northbound in the from the South Side Elevated to the rapid transit lines. morning inbound rush hours, or North Side Elevated and vice versa southbound in the evening outbound fo rmerly operated on the elevated Track Layout of Route No. 1 rush. In order that trains can be structure in the downtown area and routed in either direction between now save from 7 to 22 minutes daily Not all of the trains to and from the three-track elevated lines and for each of thousands of passengers. the south or the north use the new either the subway or the elevated A further advantage is that the subway, and, therefore, the track lay north of Seventeenth street, the track stations on the new subway are lo outs at the portals were designed layout is designed as shown in Fig. cated more conveniently with refer so that trains can be routed to or 3. This layout includes 4 crossovers. ence to important stores and office from either the subway or the ele 1 single switch and 17 interlocking buildings. ' Another is that the sub vated structure through the down signals, wh ich are controlled by an way goes under the Chi cago river, town area. The North Side Elevated all-relay route interlocking machine 254 RAILWAY SIGNALING May, 1944 in a tower north of Eighteenth street. mechanisms which are equipped with the train line thus causing an emer The details of the construction and electric locks, the control of which gency application of the brakes on operation of these interlockings will will be explained later. the entire train. be explained later in this article. The red aspect of any of the auto Where the subway under State Automatic Block Signaling matic block signals indicates Stop-and street turns east to connect with the Then-Proceed. When the train stops, elevated structure at Thirteenth The automatic block signaling in the motorman must lean out his win street, excavation was made arid bulk the subway is arranged for train dow to operate a stop release, mounted headed for a future extension south operation in one direction only, right- near the signal, which causes the trip under State street. The northbound tube of this future extension, built at a lower level to provide grade sep __/"- / - r aration, is equipped with a stub track / / with a Y connection to the present '\. // II tracks and can be used to double back +-o~" trains from the north. This track lay ...._<v // out consists of three switches and 10 ()XI'' ~/ signals controlled from an interlock // // // ing machine. / / On the 4.9 miles of double-track .. ~ ... subway between North Portal and Fig. 1-Map of the Route No. 1 of the Chicago subways South Portal, trains are ordinarily hand running on each track. The sig arm to be lowered to its normal posi operated right-hand running. In or nals are of the color-light type which tion, thus allowing the train to pass der to permit maintenance forces to display the conventional aspects red, without the brakes being applied. work on a section of track, all trains yellow or green. At each signal and in both directions can be operated on at rail level there is an automatic trip Track Capacity Determined by the other track during slack periods type train stop which is in depressed Train Speeds, Spacing Between between 2 a.m. and 5 a.m. In order to position as long as the signal displays Trains and Braking Distances sectionalize the tracks for this pur either the green or the yellow aspect, The automatic signaling was pose, there are two sets of diamond but when the signal displays the red planned to attain two objectives ; to crossovers, one just south of the sta- aspect, the trip arm is raised to a level operate the trains at the maximum Fig. 2-Track and signal plan of the interlocking at the South Portal tion at Grand avenue and the other where it will strike and operate an speeds which are practicable in con south of the station at North avenue. air valve on each car of a train, if the sideration of the spacing of stations These crossover switches are operated train is driven past the signal. Oper and the tractive effort of the equip by hand-operated switch-and-lock ation of this valve releases the air in ment, and also to get as many trains --sn------_ ~ ~ 1:!! 42 ~ lli L~ ------~2o ~cc-------4o-~- r-r 1 ~---- ~u=--.....,6:-::-zc- -:.Eo..w:!!o..subway ~ 18 28 J: :::::::=-:=:::: 44 :r .L.., 46 C 66 Tk.J ~16 __]---- 32C__ .;_ 1 -=I-:::.:IJ-0 -==-----,-+-_-4-=-=~----:=::-----:~=---~68 c· 10 1 1 I 1-1 I 1-1~ J4l J61 '5oTl "!154 '411 m Fig. 3-Track and signal plan of the interlocking at North Portal May, 1944 RAILWAY SIGNALING 255 over the line as possible by reducing an hour. On ascending grades the grades. In consideration of all these the space between trains to a mini train braking distance is shorter and, factors, the speed of trains when mum that is consistent with that re therefore, the block lengths can be descending grades is limited by rule quired to stop short of a train ahead. correspondingly shorter, thereby to certain maximums as marked on On this basis, for the normal run- automatically reducing the space be- signs along the track, and the signal- ~ ~ ~ ~ ~ ------D~--~d~----c=rO~----~c------~6~----~b~-----D------a--------~ Fig. 4-Diagram showing control limits of signals and train stop ning speed between stations th e min tween following trains to compensate ing and train-stop system include imum spacing of signals is the di s for the reduced speed when ascending special grade-time-distance controls tance required to stop a train running the g-rade. arranged so that the brakes are ap at maximum speed with an emer plied automatically if this maximum oency application of the brakes, plus Descending Grade a Different speed is exceeded.

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